As I understand it the Forces are a special case and will be one of the few professions allowed to take an immediate pension when they retire at 55. However, if you retire early, you will not be entitled to a pension until the age of 65.
Our current pension has reserved rights, therefore we should be all right. But those offered the opportunity to switch to the new pension (in 2007/8?) should look very carefully unless they know they will be staying to 55.
The switch will also possibly entail losing the tax-free gratuity, especially if you retire early. But this last point is very unclear.